Project summary: The objectives of this Pathway to Independence Award for Long Ding, Ph.D., are to expand the candidate's expertise in the field of visual perceptual decision-making and to establish a novel experimental model to fill the knowledge gap on how visual perception is affected by reward-induced internal preferences. Achieving the first objective will complement the candidate's previous training in basal ganglia physiology related to learning and neural representation of reward. Achieving the second objective will provide a launching point for the candidate to develop an independent research career, toward a long-term goal of gaining a better understanding of the basal ganglia functions in reward modulation of perception. These objectives will be accomplished in two phases. In the 2-year mentored phase, the candidate will conduct supervised research in Dr. Joshua Gold's lab at the University of Pennsylvania to identify neural correlates of external evidence-based perceptual decisions in the basal ganglia and frontal cortex, using single-unit recordings in monkeys performing a visual motion discrimination task (Aim 1). This training environment is uniquely suitable because of Dr. Gold's expertise in visual perceptual decision-making, the immediate availability of well-trained monkeys and the intellectual resources available at Penn, which is renowned for its research on vision and perception. In the next 3-year phase, the candidate's independent research will identify neural correlates of decision-making that integrates reward-induced internal preference and external evidence in the basal ganglia and frontal cortex (Aim 2). This research will be based on single- unit recordings in monkeys performing a novel visual motion discrimination task that also incorporates reward bias. The proposed research is designed to test the central hypothesis that the neural representations of external evidence and reward-induced internal preference are co-localized and incorporated in individual neurons in the basal ganglia and frontal cortex. It represents an innovative merging of established lines of research and will advance our understanding of the neural mechanisms underlying normal visual perception. Relevance to public health: The proposed research represents an important research area of visual perception and will facilitate future identification of neural targets for better treatment of patients with perceptual impairment.